Penetrating instruments such as hypodermic needles and their use in an imbibition pressure meter



June 1953 J. R. SQUIRE ETAL 2,840,069

PENETRATING INSTRUMENTS SUCH AS HYPODERMIC NEEDLES AND THEIR USE IN AN IMBIBITION PRESSURE METER Filed Sept. 22, 1955 2 Sheets-Sheet 1 a DAVID STUART ROWE ska, QW,W&MW

Attorneys June 24, 1958 J. R. SQUIRE ETAL 2,840,069

PENETRATING INSTRUMENTS SUCH AS HYPODERMIC NEEDLES AND THEIR USE IN AN IMBIBITION PRESSURE METER Filed Sept. 22, 1955 2 Sheets-Sheet 2 a I w l illlllllli \l lilllllI'IIIU lllllllllllllllllllIIIIII Attorneys i 1" r "2,840,069 .PENETRATING INSTRUMENTS SUCH I BIaI'I'roN PRESSURE 'METER' DERMIC NEEDLES AND. THEIRUSEVTIYAN! 11n- I In somebranches of science and .industry there is a need for a penetrating instrument such-as a hypodermic needle which willestablish a large areaof contact with the bodyor-substahce into'whicli the instrument i js inserted. -Such a need arises in the measurement of timbibition pressure.

The present invention provides such an instrument and consists in forming the penetrating portion of the instrument as a tube of porous-material. thebore of which does not extend through the extremity of .the penetrating portion which is pointed for incision. -The porous material is preferably sintered metal. I

This-penetrating instrument therefore difiers from a conventional hypodermic needle in that contact between the bore and the body or'substance-penetrated is-made only through the pores of the sintered metal side and end wallsofthetube. a .1 J I p Use is made of a penetrating instrument, according ,to 'the invention in the measurement of imbibition-pressure.

It has long been known that colloid gels-exert an-;appreciableattractive force for. additional water. It, is also known that the interstitial space which liesbetween the blood vessels and the body'cells ofv the human body is occupied bya groundsubstancef? v It is thought that this ground substance is-probably a'gel'and as such it should exert an attracti'veforceor imbibition pressure which may'v'ary' a'ccordingto, the condition of the body between a value greater'than normal when the body is de-hydrated,'t'o zero when the body is extremely water-logged. Such a pressure is very difiicult to measure and requires extremely sensitive apparatus for its determination; i i 1 Accordingto a further aspect of the present invention the'bore of a porous' penetrating instrument according to the invention'is open" to a chamber closed by a metal foil diaphragm which is connected 'to' means? capable ofdetecti'ng small deflections, the chamber being connected through a tap to means for applying negative pressure and provided with pressure means.

The means for detecting'small deflections preferably A penetrating instrument according to the present in- 'vention will now be described, by way of example, with reference to the accompanying drawings which also illustrate an imbibition pressure meter in which thepenetratfing instrument is employed. In the drawings:

Figure 1 is a longitudinal sectional-view of the penetrating instrument shown inserted in a mass of gelatinous substance.

J 2,840,069 Patented June, 24,,

pi Fi 7 Figure 2 is a diagrammatic representation,bfithenrn: b o pr s u e me e w h t p i afi s in t m nt and the-portion .closely'associated with-it shown/on an enlarged scale. i i

Figure 3 shows a bridge circuit for use bibition pressure meter of Figure'ZI g 7 Referring first to Figure 1 the penetrating'instrument has a penetrating portion 4 which is a tube orper u sintered metal the bore 5 of which does notextendthrough the extremity 6 of the penetrating portion which is pointed for incision in the usual manner. w p i A successful instrument-hasbeen madeinnickel but probably other metals may be used. The desired porosity of thetwallssmay be obtained in-manufacture by normal powder metallurgy techniques for example by controlling the penetrating portion should beas snrall as possible. In

such cases adequate mechanical strength eanz beiobtained by making the bore very fine. The external dimensions need not, then exceed those of hypodermic needles at present used in blood transfusion. Inother ca se s .a fine bore maybe desirable to restrict the internalvolume of the instrument; for example, in measurement work The end of the penetrating portion; remotefrom the point'may be secured-in. any convenient mountingadapted to make external connections to the :bore, i If desired the Pa t Qf'the penetrating portion adjacent the mounting .may i be 7 rendered impervious, for example; by. sealinggthe pores of the sintered metal with a suitable-material such as tin or a solder represented at 7 in Figure-l The porous area; of the penetrating portion may then be. entire1y contained within a bodyor sub'stanc I 17'prjov ided inserted sufiicientlyfar as shownin meter illustrated in Figure. 2'is provided a'tap'er socket by which it: is; detachably mountedon afriistdconical adapter 9, secured 'to orintegrallwith a.ri gid ;.block I of metal10 in which a chamberlllpf truncatedconieal shape is formed. The truncated end isopen throughthe adapter 9 to the bore of the penetrating ins A lateral passage. 12 leads to a tap l3 andlth ough theitap topressure'varying means 14. g

-The chamber llpis closed at the, large diam r end a. metal foil diaphragm 15 which s ar a;jencebyja V Phosphor bronze screw-threaded retainingring; 1 6. The centre of the metal foil diaphragm is connecte d;by ;a

spring blade18lto the finger .20 of a mechano-ele'ctronic America ype The finger .20 of the mechano-electronici transd cer valve 19 detailsof which are not illustrated is 'pflmviaeeen a diaphragm closinglthe valve envelope; Thedia'phr'agm carries within the envelopea movable anode. Deflections of the metal foil 'diaphragm15' causes movement of-fthe,

anode and a consequent changein the anode to cathode resistance of the valve 19. I

To detect this change of resistance the anode and cathode of the transducer valve 19 are connected as one arm of the Wheatstone bridge circuit shown in Figure 3 of the accompanying drawings. The other arms comprise respectively fixed resistors 25 and 26 and a variable resistor 27 forming a balancing arm, which are connected together at junctions 28, 29, 30, 31. Junctions 30 and 28 are joined respectively to positive and negative of a high tension D. C. supply, junctions 29 and 31 are joined through a sensitive galvanometer G and point 29 is grounded. The heater of the transducer valve is supplied from a source 32 through a variable resistor 33. A volt-' tion of, thevalye.

' fthlrough said pointed eirt'remitvx meter V is provided to'indicate the potential difference across the heater element *which'it is importanttokeep constant to ensure stability. f, I

tap 13,0n closing -must cause as little change of pressure in thechamber as usable. -It may be rotary as illustrated "or fafslide valveivvith a through passage adapted to-connect a pair of' p orts together in" one posi- The means "for applying negative pressure 14fmay simply comprise a reservo'irll adapted to be'raised and losvered about the datum 2 2" of the 'penetrating'instru- 'ment 8 and-fcon'riected, by ;a flexible tube 23 to the tap 13 a simple manometer tube 24 for pressure measuree 1 u v I The;system isfilled 'withsaline solution and in use the porous penetrating instrument'is thrust into a block of jelly (e ."fg. gelatin) or under the skin making a'f airly large area of contact between saline'and the surrounding i 5. An imbibition pressure meter including a penetrating-instrumentaccordingto claim 3 and further comprisuring said negative pressure through said valve to said gel. The negative "pressure is adjusted by raising orloweringthe reservoir 21 until upon closing thejtap 13 no "appreciabledeflection of the metal foil diaphragm occurs.

.Th'regis then no transfer of saline through the porous wall of the penetratinginstrument and the manometer reading givestheimbibition pressure.

The sensitive i strument prov ventioncnables imbibition pressure to be measured with ided by the present inconsiderable accuracy. It has applications in hospital work and in the chemical industry.

Another possible application of the porous penetrating instrument according totheinve'ntion which however has not yet been investigated is in the intravenous administration of] oxygen. Inexisting techniques excessively largeg'lobules of'oxygen are sometimes injected into the bloodstream and it is thought "that within instrument according to thepresent'invention betterdiffusion of oxygen" should be possible.

We claim:

for eirternal connection and extending towards but not ,A penetrat n g 1nstrumeritfsucli as/a hypodermic tlbcdlgl llhreitl the penetrating'portion of" the instrument is {a tubeot poroussintered; metal the bore of which tube, I

does not extend through. theentremity of the penetrating tene in r nt comprising in com inaii n us siiiteredimetal theb'oreof which does not oughnthe pointer! extremity, the other end imperuioius.

, 4.'A penetrating instrument according 1 to claim wherein the porous sin tered ineta lis rendered impervious by sealingsvith; a metal such as solder,

penetrating "instrument 'liaving a penetrating por- "tionlof porous tubularmaterial withan extremity pointed for incision, the hereof the tube being adapted at one end 40 chamber, means for detecting small deflections and means for affecting said sensitive detecting means by deflections of said diaphragm, r I r 6. An imbibition pressure meter comprising penetrating means for porous tubular material closed .at one extremity andpointed for incision, a rigid body block having a portion supportingsaid penetrating means, a valve rigidly supported by said body block, a chamber within said body block closedby-a metal foil diaphragm and open to the bore of said penetrating means, there being a passage connecting said chamber to said valve, means for applying negative pressure, means for measuring said negative p'r'essure,means for connecting said means for applying and measuring said negative pressure through said valve to said chamber, means for detecting small deflections and means for affecting said sensitive detecting means 'bydeflections of said diaphragm.

7. An imbi'bition pressure meter comprising penetrating means "of'porous tubular material closed at one extremity and pointed for incision, a rigid body block havbeing a passage connecting said chamber to said valve, means for applying negative pressure, means for measur-.

ing said negative pressure, means for connecting said meansfo'rapplying and measuring said negative pressure through said valve to said chamber, means for'detecting small deflections and means for affecting said sensitive detecting means by'deflections of said diaphragm.

8. An imbibition pressure meter comprising penetrating means of porous tubular material closed at-one extremity" and pointed for incision, a rigid body block having a portion" supporting said penetrating means, a valve rigidly supported by said body block; a chamber within said body block closed by a metal foil diaphragm and open to the bore of said penetrating means, there being a passage connecting said chamber to said valve, means for applying negative pressure, means for measuring said negative pressure, means for connecting said means for applying and measuring said negative pressure 1 through said valve to saidchamber, a mechano-electronic transducer valve rigidly mounted with respect to said body block and having a movable anode, means for moving said movable anode responsive to deflections of said diaphragm.

' 1 References Cited in the file of this patent UNITED STATES PATENTS 2,600,324 Rappaport June 10, 1952 

